1. Field of the Invention
The present invention relates to a spindle device and, more particularly, to the spindle device provided with externally pressurized gas bearings or combined externally pressurized gas-magnetic bearings and also to a machining apparatus equipped with the same.
2. Description of the Prior Art
In recent years, a highly efficient, highly precise machining has drawn keen attentions in the field of a mold machining field. In order to implement such a machining, it is necessary to use a spindle device capable of accomplish a high speed rotation with high rotational precision and having a static stiffness and a dynamic stiffness, and it is also required to perform the machining under optimum machining conditions by detecting the status of machining.
To meet these requirements, the applicant has suggested a hybrid type non-contact bearing assembly in which externally pressurized gas bearings and magnetic bearings are combined together as disclosed in the Japanese Laid-open Patent Publication No. 11-013759. According to this suggestion, by utilizing an excellent dynamic stiffness and a rotational precision, both exhibited by the externally pressurized gas bearing, and an excellent static stiffness exhibited by the magnetic bearing, a compact bearing assembly making advantages of those different types of bearings can be obtained. Also, measurement of a machining load of a machine tool for detection of the machining status is generally carried out by a system in which the load during the machining is inferred from a value measured of a motor output for rotating the main shaft.
However, the system of inferring the load during the machining in reference to the motor output measured value as hereinabove described has a problem in that a measuring instrument designed exclusively for that purpose is required, resulting in increase of the system cost.
Also, the system of detecting the machining status in reference to the motor output measured value is incapable of detecting the machining status associated with the frequency of rotation of the main shaft.
Apart therefrom, in the spindle device in which the main shaft is rotatably supported by the magnetic bearings, a system has also been suggested to detect the machining status in reference to the excitation current supplied to the magnetic bearings. However, mere support of the main shaft solely by means of the magnetic bearings makes it difficult to secure a high precision of high speed rotation and a high dynamic stiffness. Also, in the system of detecting the machining status in reference to the excitation current supplied to the magnetic bearings, an attempt has been made to detect the machining status associated with the frequency by the use of a frequency filter. However, to detect the machining status with respect to a number of frequency regions requires the use of an increased number of frequency filters, resulting in complicated structure and increase of the cost.
In order to achieve a highly efficient, highly precise machining, the spindle device is required of a type capable of achieving a high speed rotation with a high rotational precision. To satisfy this requirement, a non-contact bearing is suitable. The spindle device of a non-contact bearing supported type is available in some types for example, a spindle device utilizing an externally pressurized gas bearing and a spindle device utilizing a magnetic bearing. The spindle device with the externally pressurized gas bearing has a rotational precision generally in the order of {fraction (1/100)}xcexcm and is therefore suited for the highly precise machining, but has a problem in that the static stiffness and the load bearing capacity are small. On the other hand, the spindle device with the magnetic bearing is excellent in terms of dynamic stiffness and load bearing capacity, but has a low accuracy of rotation of the main shaft. This is because the accuracy of rotation of the main shaft exhibited by the magnetic bearing depends on the resolution of a sensor disposed for detecting the position of the main shaft.
In general, the highly efficient, highly accurate machining is carried out in two stages including rough and finish machining processes. During the rough machining process, the amount of material that is machined per unitary time is increased to achieve a highly efficient machining, but during the finish machining process, the amount of the material to be machined is conversely reduced to achieve a highly precise machining process. For this reason, during the rough machining process, the load acting on the main shaft tends to increase and, therefore, the spindle device must have such a spindle performance requiring the stiffness and the load bearing capacity while rotation with a high precision is required during the finish machining process.
The combined externally pressurized gas-magnetic bearing assembly suggested in the previously discussed Japanese Laid-open Patent Publication No. 11-013759 is of a type effective to satisfy those requirements.
However, the combined externally pressurized gas-magnetic bearing assembly has characteristics peculiar to the externally pressurized gas bearing and those peculiar to the magnetic bearing and, where the sensor for the magnetic bearing has a low resolution, since the rotational precision of the main shaft depends on this resolution, a high rotational precision exhibited by the externally pressurized gas bearing cannot be effectively utilized.
Also, although the combined externally pressurized gas-magnetic bearing assembly of the type discussed above is a non-contact bearing, there is the possibility that the main shaft may contact a bearing surface in the event that an excessive load acts. To avoid such a contact of the main shaft, a protective bearing such as a rolling bearing has hitherto been employed in the prior art spindle device equipped with the magnetic bearing. However, since the combined externally pressurized gas-magnetic bearing assembly is of a design wherein the externally pressurized gas bearing is formed in the magnetic bearing unit, the gap between the main shaft in the bearing unit and a magnetic bearing stator is so small, for example, not greater than some tens microns and, therefore, the protective bearing in the form of the rolling bearing generally used in the spindle device with the magnetic bearing cannot be used. Also, since the externally pressurized gas bearing surface forms a part of an electromagnet for the magnetic bearing, material for the externally pressurized gas bearing surface is limited to a ferromagnetic substance having no lubricating capability. For this reason, in the event that an excessive load is applied to the spindle device, contact between the main shaft and the bearing surface brings about a detrimental influence on the bearing unit.
Also, in the spindle device utilizing the non-contact bearing such as the previously discussed combined externally pressurized gas-magnetic bearing assembly or externally pressurized gas bearing, as shown in FIG. 29, the main shaft 4 has a collar 4a formed therein, opposite end faces of the collar 4a being generally utilized to form axial bearing surfaces.
In the spindle device utilizing such a non-contact bearing, as discussed with reference to FIG. 29, the axial position (C dimension) of a tip of a machining tool 11 fitted to the main shaft varies depending on the dimension (B dimension) of a housing 5 as measured from the position P, at which the spindle is fitted and the collar 4a of the main shaft 4 and the dimension (A dimension) of the main shaft 4 as measured from the collar 4a of the main shaft and the tip of the machining tool 11. The spindle fitting position P represents the position at which the housing 5 is mounted on a spindle support bench 76 that is reciprocally driven by a spindle positioning mechanism 54.
When the spindle device of the structure described is driven at a high speed, the temperature of any of the main shaft 4 and the housing 5 increases as a result of a loss (windage loss) at the externally pressurized gas bearing unit and the axial position (C dimension) of the tip of the machining tool changes with the amount of thermal expansion in a direction axially of the main shaft that is brought about by increase of the temperature of the main shaft and the housing. For this reason, it has been difficult to achieve a highly precise machining.
In addition, the combined externally pressurized gas-magnetic bearing assembly has characteristics that are generally exhibited by the externally pressurized gas bearing and the magnetic bearing, respectively, as hereinbefore described. Accordingly, where the sensor for the magnetic bearing has a low resolution, the rotational precision of the main shaft depends on this resolution and, therefore, the high rotational precision generally exhibited by the externally pressurized gas bearing cannot be effectively utilized.
In view of the foregoing, the present invention has been devised to substantially eliminate the above described problems and is intended to provide an improved spindle device equipped with the combined externally pressurized gas-magnetic bearing assembly, and an improved machining apparatus utilizing the same, both of which can rotate at a high speed with high rotational precision.
To facilitate a better understanding of the present invention, first to sixth structures of the present invention will be made using reference numerals used in FIG. 1. The spindle device according to the first structure of the present invention is provided with at least one combined externally pressurized gas-magnetic bearing assembly (6 to 9) for rotatably supporting a main shaft (4), having a machining tool (11) fitted to a tip thereof, and also with a spindle drive source (10) for rotating the main shaft (4). The combined externally pressurized gas-magnetic bearing assembly comprises at least one externally pressurized gas bearing (6A to 9A) and at least one magnetic bearing (6B to 9B) combined together. The spindle device includes an electric current detecting means (11 to 18) for detecting an excitation current for the magnetic bearing (6B to 9B), and a machining status determining means (19) for determining a machining status performed by the machining tool (11) in reference to a current value detected by the current detecting means (11 to 18).
According to this structure, the machining status can be grasped by the machining status determining means (19) in reference to the current detected value of the energization current supplied to the magnetic bearing (6B to 9B) in the combined externally pressurized gas-magnetic bearing assembly (6 to 9). In other words, in the event that the main shaft (4) tends to displace in a radial direction by the effect of a load acting on the machining tool (11) during the machining operation, the energization current of the magnetic bearings (6B to 9B) is varied by a control function possessed by the magnetic bearing (6B to 9B) so as to restore the displacement. For this reason, the machining status such as, for example, wear of the machining tool, damage to the machining tool and/or improper machining can be determined in reference to the energization current. Thus, the provision of the machining status determining means (19) is effect to increase the function of the combined externally pressurized gas-magnetic bearing assembly (6 to 9), that is, to accomplish a high speed rotation and, in combination of a high rotational precision, a high static stiffness and a high dynamic stiffness, the machining is possible under optimum machining conditions while the machining status is detected, wherefore a highly precise machining can be effected at a high efficiency while merits of the combined externally pressurized gas-magnetic bearing assembly (6 to 9) are utilized. Moreover, for detectors the use of the current detecting means (15 to 18) of the energization current of the magnetic bearing (6B to 9B) is sufficient, and no load measuring device need be used outside, and as compared with detection of the current flowing through the motor, simplification can be achieved with reduction in cost.
In a preferred embodiment of the first structure of the present invention, the current detecting means (15 to 18) is provided in a spindle controller (3) for controlling the combined externally pressurized gas-magnetic bearing assembly (6 to 9). With this design, the provision of the current detecting means (15 to 18) in the spindle controller (3) is effective to render it to be compact and easy to handle.
Also, in another preferred embodiment of the present invention, the machining status determining means (19) includes a current smoothing unit for smoothing the current value detected by the current detecting means, and a machining status determining unit for converting a smoothed output from the current smoothing unit into a static load acting on the main shaft and for determining the machining status in reference to a result of calculation of the static load. Thus, by grasping the machining status in reference to the result of conversion of the static load, monitoring of the machining status necessary for control can be simply and precisely accomplished without being affected by change in load occurring in a minute time and any external disturbance.
The spindle device according to the second structure of the present invention is provided with at least one combined externally pressurized gas-magnetic bearing assembly (6 to 9) for rotatably supporting a main shaft (4), having a machining tool (11) fitted to a tip thereof and, also, with a spindle drive source (10) for rotating the main shaft (4). The combined externally pressurized gas-magnetic bearing assembly (6 to 9) includes at least one externally pressurized gas bearing (6A to 9A) and at least one magnetic bearing (6B to 9B) combined together. The spindle device includes a displacement detecting means (28, 38) for detecting a displacement of the main shaft (4), and a machining status determining means (19) for determining a machining status performed by the machining tool (11) in reference to a displacement value detected by the displacement detecting means (28, 38).
According to this structure, when the main shaft (4) undergoes displacement by the effect of a load acting on the machine tool (11) during the machining operation, the displacement detecting means (28, 38) detects such displacement. For this reason, the machining status can be determined in reference to the displacement value detected by the displacement detecting means (28, 38). Accordingly, the provision of the machining status determining means (19) is effect to increase the function of the combined externally pressurized gas-magnetic bearing assembly (6 to 9), that is, to accomplish a high speed rotation and, in combination of a high rotational precision, a high static stiffness and a high dynamic stiffness, the machining is possible under optimum machining conditions while the machining status is detected, wherefore a highly precise machining can be effected at a high efficiency while merits of the combined externally pressurized gas-magnetic bearing assembly (6 to 9) are utilized. Moreover, since the displacement detecting means (28, 38) represents a detecting means generally used in the magnetic bearing (6B to 9B) for controlling the magnetic bearing (6B to 9B), the machining status can be grasped with no dedicated detecting means used and, therefore, the machining precision can be increased at a reduced cost.
In the embodiment according to any one of the first and second structures of the present invention, the machining status determining means (19) may include a frequency analyzing unit for frequency analyzing an output from the current detecting means (15 to 18) or the displacement detecting means (28, 38), and a machining status determining unit for determining the machining status in reference to an amplitude of each of frequency components during a machining, which components are outputted from the frequency analyzing unit.
The load acting on the machining tool is represented by a vibration of the machining tool in view of the natural vibration of the machining tool, a work and the machine tool or the number of revolution of the main shaft, and the machining status such as damage to the machining tool gives rise to a peculiar tendency in the frequency of vibration depending on the type of machining defects. For this reason, by employing the previously described embodiment in which the use has been made of the frequency analyzing unit in combination with the machining status determining unit for determining the machining status in reference to the amplitude of each of the frequency components during the machining, a highly precise machining status which cannot be achieved with detection of the load-in which the frequency components are averaged can be achieved. Also, since the frequency analysis is carried out, analysis of a number of frequency regions is possible with a simplified construction as compared with the use of frequency filters.
In a preferred embodiment according to any one of the first and second structures of the present invention, the spindle drive source (10) includes a motor built in a housing (10) in which the combined externally pressurized gas-magnetic bearing assembly (6 to 9) is housed. Thus, in the spindle device having the spindle drive source built therein, the various effects brought about by the previously described structures of the present invention can be effectively appreciated.
Also, In a preferred embodiment according to any one of the first and second structures of the present invention, the use is made of a spindle controller (3) for controlling the externally pressurized gas-magnetic bearing assembly (6 to 9), and an external output means (44) for outputting to an outside of the spindle controller (3) one of a current value detected by the current detecting means (15 to 18), a smoothed output from a current smoothing unit, and an amplitude of each of frequency components outputted from a frequency analyzing unit. Thus, the provision of the external output means (44) is effective to allow the load on the machining tool (11) to be monitored outside the spindle controller (3). By way of example, by monitoring the load on the machining tool (11) by means of a numerical control device (14) of the machining apparatus (13) equipped with the spindle device (1), an independent information processing means or the like, the machining status can be determined.
A remotely machining status determining spindle device according to a third structure of the present invention includes the spindle device (1) of any one of the previously described structures of the present invention, an information processing means (58) installed at a remote place distant from the spindle device (1), a communication means (58) for communicating one of an output from a machining status determining means (19) of the spindle device (1), a current value detected by the current detecting means (15 to 18), a smoothed output from a current smoothing unit, and an amplitude of each of frequency components outputted from a frequency analyzing unit, to an information processing means (72) installed at the remote place through a communication line (59). The information processing means (72) has a function of performing a predetermined process on the communicated information.
By providing the spindle device with a capability of performing communication through the communication line (59), the load on the machining tool and the machining status thereof can be grasped at the remote place and it is possible to intensively manage and control a number of spindle devices and machining tools at the remote place.
The spindle device (1) according to the fourth structure of the present invention is provided with at least one combined externally pressurized gas-magnetic bearing assembly (6 to 9) for rotatably supporting a main shaft, having a machining tool (11) fitted to a tip thereof, a spindle drive source (10) for rotating the main shaft (4) and a spindle controller (3) for controlling the combined externally pressurized gas-magnetic bearing assembly (6 to 9) of a type in which at least one externally pressurized gas bearing (6A to 9A) and at least one magnetic bearing (6B to 9B) combined together. The spindle device (1) includes an externally command responsive ON-OFF means (20) for turning energization of the magnetic bearing (6B to 9B) on and off in response to a command supplied from an outside of the spindle controller (3).
According to this structure, when the magnetic bearing (6B to 9B) is turned off, the main shaft (4) can be rotatably supported only by the externally pressurized gas bearing (6A to 9A) of the combined externally pressurized gas-magnetic bearing (6 to 9), but when the magnetic bearing (6B to 9B) are turned on, the main shaft (4) can be rotatably supported by both the externally pressurized gas bearing (6A to 9A) and the magnetic bearing (6B to 9B). The support by both bearings (6A to 9A, 6B to 9B) and the support only by the externally pressurized gas bearing (6A to 9A) can be switched one over the other in response to the command supplied from the outside of the spindle controller (3). For this reason, an optimum bearing set-up appropriate to a desired machining condition can be carried out at any desired time, allowing the combined externally pressurized gas-magnetic bearing assembly (6 to 9) to exhibit its full function to thereby secure an increased high rotational precision.
In a preferred embodiment of the fourth structure of the present invention, the external command for turning the energization on and off is supplied from a numerical control device (14) of a machining apparatus (13) equipped with the spindle device (1). Thus, by applying the energization ON-OFF command from the numerical control device (14), the optimum bearing can be set quickly according to the machining condition that varies with progress of the machining operation.
A machining apparatus according to the fifth structure of the present invention is a machining apparatus equipped with the spindle device (1) having the combined externally pressurized gas-magnetic bearing assembly (6 to 9) according the fourth structure of the present invention. This machining apparatus includes a numerical control device (14) for controlling a machine section (13a) of the machining apparatus (13) and an energization ON-OFF command generating means (45) for applying an energization ON-OFF command to the external command responsive ON-OFF means (20).
Preferably, the external command for turning the energization on and off is a command that turns on the magnetic bearing during a rough machining the magnetic bearing, but turns the magnetic bearing off during a finish machining. In this way, a high efficiency can be achieved during the rough machining process while a high precision can be achieved during the finish machining process, and, accordingly, a highly efficient, high precise machining can be achieved.
A remote controlled spindle device according to the sixth structure of the present invention includes any one of the spindle devices (1) equipped with at least one combined externally pressurized gas-magnetic bearing assembly according to the fourth structure of the present invention, in combination with a information processing means (72) installed at a remote place distant from the spindle controller (3) and capable of communicating with the spindle controller (3) through a communication line (59). The information processing means (72) has a function of applying a command to an external command responsive ON-OFF means (20). In this structure, change of the bearing setting can be carried out at the remote place and an intensive change of the bearing setting can be carried out at the remote place with respect to a number of the spindle devices
The seventh structure of the present invention will now be described using reference numerals used in FIGS. 19 and 20 for the purpose of facilitating a better understanding thereof. A spindle device (1A) according to the seventh structure is equipped with at least one combined externally pressurized gas-magnetic bearing assembly (6, 7) in which at least one externally pressurized gas bearing (6a, 7A) and at least one magnetic bearing (6B, 7B) are combined together. The spindle device (1A) includes a main shaft (4) rotatably supported by the combined bearing assembly (6, 7), and a housing (5) accommodating the combined bearing assembly (6, 7) and the main shaft (4) therein, slide members (47) disposed within the housing (5) and positioned adjacent the main shaft (4) with a radial gap (d3) defined between them and the main shaft (4). The radial gap (d3) has a size smaller than a radial bearing gap (d1) defined by the externally pressurized gas bearing (6A, 7A) and the magnetic bearing (6B, 7B) both forming respective part of the combined bearing assembly (6, 7). Each of the slide members (47) is made of carbon or graphite.
According to this structure, even when an excessive load acts on the main shaft (4) and a mechanical contact occurs between the main shaft (4) and a member on a stationary side, such mechanical contact would be a contact between the slide members (47) and the main shaft (4). Also, since the slide members are made of carbon or graphite, the coefficient of friction thereof is small. For this reason, neither the main shaft (4) nor the bearing surfaces (6Aa, 7Aa) and the slide members (47), all employed in the spindle device (1A), will be impaired by the previously described contact.
In a preferred embodiment of the seventh structure discussed above, the magnetic bearing (6B, 7B) of the combined bearing assembly (6, 7) has a bearing core (23) which defines an externally pressurized gas bearing surface (6Aa, 7Aa). Where the externally pressurized gas bearing surface (6Aa, 7Aa) is defined by the core (23) of the magnetic bearing (6B, 7B), the bearing structure can be simplified, but material for the externally pressurized gas bearing surface (6Aa, 7aa) is limited to a ferromagnetic metal which has normally no lubricating property and, therefore, it is important to avoid any possible contact thereof with the main shaft (4). For this reason, it is effective to avoid any possible damage to the main shaft (4) by allowing the latter to be supported by the slide members (47).
In a preferred embodiment of the seventh structure of the present invention, the slide members (47) are disposed on respective side of one or an array of combined externally pressurized gas-magnetic bearing assemblies (6, 7) adjacent respective opposite ends of the main shaft (4). By positioning the slide members (47) on respective sides of the combined externally pressurized gas-magnietic bearing assembly or assemblies (6, 7) adjacent the opposite ends of the main shaft (4), the main shaft (4) can be assuredly supported by the slide members (47) even when the main shaft (4) tends to tilt under the influence of an excessive radial load, thereby avoiding any possible direct contact of the main shaft (4) with the bearing surface (6Aa, 7Aa).
Preferably, the slide member has a Shore hardness of not smaller than 50, a bending strength of not smaller than 400 Kgf/cm2, a compressive strength of not smaller than 700 Kgf/cm2 and a coefficient of thermal expansion of not greater than 5xc3x9710xe2x88x926. The use of the specific material for the slide members (47) having such a hardness, bending strength and a compressive strength, any possible damage to the slide members (47) which would be brought about by contact with the main shaft (4) can advantageously be avoided. Also, selection of the coefficient of thermal expansion of the slide members (47) within the specific range described above is advantageous in that it becomes equal to or smaller than the coefficient of thermal expansion of a soft magnetic metal generally used as a material for the cores (23) of the magnetic bearings (6B, 7B) of the combined externally pressurized gas-magnetic bearing assembly (6, 7) and, therefore, expansion of the inner diameter of the slide members (47) as a result of thermal expansion will become equal to or smaller than that of the cores (23). For this reason, even when an excessive load acts on the main shaft (4) during increase of temperature, it is effectively supported by the slide members (47). It is to be noted that the carbon or graphite used as material for the slide members (47) are effective to satisfy the above described requirements.
The eighth structure of the present invention will now be described using reference numerals used in FIGS. 22 for the purpose of facilitating a better understanding thereof. The spindle device (1C) according to the eighth structure of the present invention makes use of the spindle device including a main shaft (4), at least one combined externally pressurized gas-magnetic bearing assembly (6, 7) comprising at least one externally pressurized gas bearing (6A, 7A) and at least one magnetic bearing (6B, 7B) combined together for supporting the main shaft (4) rotatably, and a housing (5) accommodating the main shaft (4) and the combined bearing assembly (6, 7) therein.
The spindle device of the eighth structure comprises a temperature measuring means (77) for measuring a temperature of the housing (5) and a temperature measurement associated output means (78) for obtaining a predetermined output in reference to a temperature value detected by the temperature measuring means (77). The predetermined output from the temperature measurement associated output means (78) is represented by at least one of (i) an output from the temperature measuring means (77) (that is, the temperature measured value), (ii) a converted value obtained by converting the temperature value measured by the temperature measuring means (77) into an axial position of a tip of the main shaft (4) or an axial position of a member fitted to the tip of the main shaft (4), according to a predetermined thermal displacement calculation, and (iii) an abnormality signal determined by comparing the temperature value measured by the temperature measuring means (77) or the converted value with a predetermined value.
The converted value referred to above may be any value that can be handled as a position data and, for example, a value proportional to the data representative of the actual position or a value representative of the amount of displacement from a reference position can be equally employed therefore.
According to this structure discussed above, even when the temperature of the spindle device (1C) increases as a result of generation of heat resulting from a loss (windage loss) of the externally pressurized gas bearing, the amount of feed can be compensated by the utilization of the temperature measured value outputted from the temperature measurement associated output means (78) and the converted value of the axial position that has been calculated according to the thermal displacement calculation, thereby allowing the work to be machined with high precision. In the event that the output from the temperature measurement associated output means (78) is an abnormality signal, a suitable procedure such as immediate halt of the spindle device (1C) can be carried out quickly by detecting the abnormality signal outside the spindle controller at the time of occurrence of abnormality in the spindle device such as an excessive increase of the housing temperature.
In a preferred embodiment of the eighth structure of the present invention, the main shaft (4) is made of a material having a low coefficient of thermal expansion. The axial position of the tip of the main shaft (4) or the member (11) such as the machining tool fitted to the tip of the main shaft is associated with both the thermal expansion of the housing (5) and that of the main shaft (4). However, since the main shaft (4) is driven at a high speed, it is difficult to achieve the temperature measurement. For this reason, the material having a low coefficient of thermal expansion is employed for the main shaft (4) while the position of the tip of the main shaft (4) or the member (11) fitted to the tip of the main shaft (4) is compensated for displacement resulting from the thermal expansion by measuring the temperature of the housing (5). By so doing, an accurate compensation for the thermal expansion can be easily accomplished, allowing a highly precise machining to be implemented.
In a preferred embodiment of the eighth structure, the use is made of an external output means (87) for outputting the predetermined output from the temperature measurement associated output means (78) to an outside of the spindle device (1C). The provision of the external output means (87) in this way allows the numerical control device (14) or any other information processing means, employed in the machining apparatus (13) equipped with the spindle device (1C), to provide the output with which thermal displacement compensation of the spindle position and that to be effected at the time of abnormal temperature can easily be performed.
In a further preferred embodiment of the eighth structure of the present invention, the external output means (87) can communicate with the outside of the spindle device (1C) through a communication line (59). Allowing the external output means to communicate with the outside of the spindle device through the communication line (59) makes the remote information processing means installed at the remote place to monitor the status of thermal displacement of the spindle device (1C), to apply a suitable command and to perform a statistics processing.
In a further preferred embodiment of the eighth structure of the present invention, the temperature measurement associated output means (78) outputs a digital signal. Allowing the temperature measurement associated output means to output the digital signal makes it possible for the digital signal to be handled easily.
In a still further preferred embodiment of the eighth structure of the present invention, the use is made of a writing means (80) for causing the temperature value, outputted from the temperature measurement associated output means (78), or an output of the converted value from the temperature measurement associated output means (78), to be inputted to and stored in a storage means (79).
Where the use is made of the writing means (80) and the storage means (79), a reading means (81) may be employed for outputting data, stored in the storage means (79), outputted from the storage means (79) in response to a command applied from the outside of the spindle device (1C). By allowing the stored data to be outputted in response to the command from the outside, the stored data of the storage means (79) can easily be handled.
In a still further preferred embodiment of the eighth structure of the present invention, the use is made of a cooling means (73) for cooling the housing (5) in which the main shaft (4) is installed, and a cooling control means (82) for controlling an cooling operation of the cooling means (73) in response to the output from the temperature measurement associated output means (78). By controlling the cooling means (73) with the output associated with the result of temperature measurement, the housing (5) can be properly cooled in an easy fashion.
In a still further preferred embodiment of the eighth structure of the present invention, a spindle positioning mechanism (54) is employed for moving the housing (4) with the main shaft (4) therein in a direction axially of the main shaft (4). A temperature compensating means (83) is also employed for controlling the spindle positioning mechanism (54) according to the temperature value or the converted value outputted from the temperature measurement associated output means (78). Where the spindle positioning mechanism (54) is thus employed, and by performing a temperature compensation control of the spindle position in reference to the temperature measured value or its converted value, the work can be highly precisely machined.
The ninth structure of the present invention is directed to a mold machining apparatus employing the spindle device according to the previously described first structure of the present invention.
The tenth structure of the present invention is directed to a mold machining apparatus employing the spindle device according to the previously described second structure of the present invention.
The eleventh structure of the present invention is directed to a mold machining apparatus employing the spindle device according to the previously fourth structure of the present invention.
The twelfth structure of the present invention is directed to a mold machining apparatus employing the spindle device according to the previously described seventh structure of the present invention.
In describing preferred embodiments of any one of the ninth to twelfth structures of the present invention, reference numerals shown in FIG. 26 are utilized to facilitate a better understanding thereof. The spindle drive source (19) for driving the main shaft (4) is preferably employed in the form of a motor built in the housing (5) in which the main shaft (4) is rotatably installed.
In a preferred embodiment of any one of the ninth and tenth structure of the present invention, the use is made of a communication means (58) for transmitting the machining status determined by the machining status determining means (19) to a remote place through a communication line (59). According to this feature, since the spindle device has a capability of performing communication through the communication line (59), not only can the machining status such as, for example, the load acting on the machining tool be determined at the remote place, but also a number of the spindle devices in the mold machining apparatuses at remote places can be controlled and supervised intensively.
Also, in a further preferred embodiment of any one of the eleventh and twelfth structures of the present invention which will be described using reference numerals employed in FIGS. 27 and 28, a communication means(58) is utilized for transmitting the output from the temperature measurement associated output means (78) to a remote place through a communication line (59). By so doing, the thermal displacement status resulting from the temperature of the housing (5) and temperature change thereof can be grasped at the remote place and, therefore, an intensive control is possible at the remote place.